[tip: x86/platform] x86/cpu: Remove M486/M486SX/ELAN support

tip-bot2 for Ingo Molnar
2026-03-30T07:06:01Z

The following commit has been merged into the x86/platform branch of tip:

Commit-ID: 7d246d15b140cf99eb7cc89b8cca9ef9e3a85660
Gitweb: https://git.kernel.org/tip/7d246d15b140cf99eb7cc89b8cca9ef9e3a85660
Author: Ingo Molnar <mingo@kernel.org>
AuthorDate: Sun, 14 Dec 2025 09:46:49 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 30 Mar 2026 08:54:32 +02:00

x86/cpu: Remove M486/M486SX/ELAN support

In the x86 architecture we have various complicated hardware emulation
facilities on x86-32 to support ancient 32-bit CPUs that very very few
people are using with modern kernels. This compatibility glue is sometimes
even causing problems that people spend time to resolve, which time could
be spent on other things.

As Linus recently remarked:

> I really get the feeling that it's time to leave i486 support behind.
> There's zero real reason for anybody to waste one second of
> development effort on this kind of issue.

Implement the first step and remove M486/M486SX/ELAN support:

CONFIG_M486SX
CONFIG_M486
CONFIG_MELAN

[ There's no recent M486=y kernel package for any mainstream x86
32-bit distribution available that I've been able to find, so
actual users should not be impacted, and any legacy users can
keep using older kernels. ]

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ahmed S. Darwish <darwi@linutronix.de>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20251214084710.3606385-2-mingo@kernel.org
---
arch/x86/Kconfig | 10 +--------
arch/x86/Kconfig.cpu | 42 ++++++--------------------------
arch/x86/Makefile_32.cpu | 2 +--
arch/x86/include/asm/vermagic.h | 6 +-----
4 files changed, 9 insertions(+), 51 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e2df1b1..6627b6d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -446,11 +446,6 @@ config SMP
uniprocessor machines. On a uniprocessor machine, the kernel
will run faster if you say N here.

- Note that if you say Y here and choose architecture "586" or
- "Pentium" under "Processor family", the kernel will not work on 486
- architectures. Similarly, multiprocessor kernels for the "PPro"
- architecture may not work on all Pentium based boards.
-
People using multiprocessor machines who say Y here should also say
Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
Management" code will be disabled if you say Y here.
@@ -2771,11 +2766,6 @@ menuconfig APM
manpage ("man 8 hdparm") for that), and it doesn't turn off
VESA-compliant "green" monitors.

- This driver does not support the TI 4000M TravelMate and the ACER
- 486/DX4/75 because they don't have compliant BIOSes. Many "green"
- desktop machines also don't have compliant BIOSes, and this driver
- may cause those machines to panic during the boot phase.
-
Generally, if you don't have a battery in your machine, there isn't
much point in using this driver and you should say N. If you get
random kernel OOPSes or reboots that don't seem to be related to
diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index f928cf6..0239e5f 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -8,19 +8,18 @@ choice
This is the processor type of your CPU. This information is
used for optimizing purposes. In order to compile a kernel
that can run on all supported x86 CPU types (albeit not
- optimally fast), you can specify "486" here.
+ optimally fast), you can specify "586" here.

- Note that the 386 is no longer supported, this includes
+ Note that the 386 and 486 is no longer supported, this includes
AMD/Cyrix/Intel 386DX/DXL/SL/SLC/SX, Cyrix/TI 486DLC/DLC2,
- UMC 486SX-S and the NexGen Nx586.
+ UMC 486SX-S and the NexGen Nx586, AMD ELAN and all 486 based
+ CPUs.

The kernel will not necessarily run on earlier architectures than
the one you have chosen, e.g. a Pentium optimized kernel will run on
a PPro, but not necessarily on a i486.

Here are the settings recommended for greatest speed:
- - "486" for the AMD/Cyrix/IBM/Intel 486DX/DX2/DX4 or
- SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5D or U5S.
- "586" for generic Pentium CPUs lacking the TSC
(time stamp counter) register.
- "Pentium-Classic" for the Intel Pentium.
@@ -46,20 +45,6 @@ choice
See each option's help text for additional details. If you don't know
what to do, choose "Pentium-Pro".

-config M486SX
- bool "486SX"
- depends on X86_32
- help
- Select this for an 486-class CPU without an FPU such as
- AMD/Cyrix/IBM/Intel SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5S.
-
-config M486
- bool "486DX"
- depends on X86_32
- help
- Select this for an 486-class CPU such as AMD/Cyrix/IBM/Intel
- 486DX/DX2/DX4 and UMC U5D.
-
config M586
bool "586/K5/5x86/6x86/6x86MX"
depends on X86_32
@@ -188,14 +173,6 @@ config MWINCHIP3D
stores for this CPU, which can increase performance of some
operations.

-config MELAN
- bool "AMD Elan"
- depends on X86_32
- help
- Select this for an AMD Elan processor.
-
- Do not use this option for K6/Athlon/Opteron processors!
-
config MGEODEGX1
bool "GeodeGX1"
depends on X86_32
@@ -292,12 +269,12 @@ config X86_L1_CACHE_SHIFT
int
default "7" if MPENTIUM4
default "6" if MK7 || MPENTIUMM || MATOM || MVIAC7 || X86_GENERIC || X86_64
- default "4" if MELAN || M486SX || M486 || MGEODEGX1
+ default "4" if MGEODEGX1
default "5" if MWINCHIP3D || MWINCHIPC6 || MCRUSOE || MEFFICEON || MCYRIXIII || MK6 || MPENTIUMIII || MPENTIUMII || M686 || M586MMX || M586TSC || M586 || MVIAC3_2 || MGEODE_LX

config X86_F00F_BUG
def_bool y
- depends on M586MMX || M586TSC || M586 || M486SX || M486
+ depends on M586MMX || M586TSC || M586

config X86_INVD_BUG
def_bool y
@@ -305,7 +282,7 @@ config X86_INVD_BUG

config X86_ALIGNMENT_16
def_bool y
- depends on MWINCHIP3D || MWINCHIPC6 || MCYRIXIII || MELAN || MK6 || M586MMX || M586TSC || M586 || M486SX || M486 || MVIAC3_2 || MGEODEGX1
+ depends on MWINCHIP3D || MWINCHIPC6 || MCYRIXIII || MK6 || M586MMX || M586TSC || M586 || MVIAC3_2 || MGEODEGX1

config X86_INTEL_USERCOPY
def_bool y
@@ -338,11 +315,10 @@ config X86_MINIMUM_CPU_FAMILY
default "64" if X86_64
default "6" if X86_32 && (MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MVIAC3_2 || MVIAC7 || MEFFICEON || MATOM || MK7)
default "5" if X86_32 && X86_CX8
- default "4"

config X86_DEBUGCTLMSR
def_bool y
- depends on !(MK6 || MWINCHIPC6 || MWINCHIP3D || MCYRIXIII || M586MMX || M586TSC || M586 || M486SX || M486) && !UML
+ depends on !(MK6 || MWINCHIPC6 || MWINCHIP3D || MCYRIXIII || M586MMX || M586TSC || M586) && !UML

config IA32_FEAT_CTL
def_bool y
@@ -378,7 +354,7 @@ config CPU_SUP_INTEL
config CPU_SUP_CYRIX_32
default y
bool "Support Cyrix processors" if PROCESSOR_SELECT
- depends on M486SX || M486 || M586 || M586TSC || M586MMX || (EXPERT && !64BIT)
+ depends on M586 || M586TSC || M586MMX || (EXPERT && !64BIT)
help
This enables detection, tunings and quirks for Cyrix processors

diff --git a/arch/x86/Makefile_32.cpu b/arch/x86/Makefile_32.cpu
index a3dda95..7c9898c 100644
--- a/arch/x86/Makefile_32.cpu
+++ b/arch/x86/Makefile_32.cpu
@@ -10,8 +10,6 @@ else
align := -falign-functions=0 -falign-jumps=0 -falign-loops=0
endif

-cflags-$(CONFIG_M486SX) += -march=i486
-cflags-$(CONFIG_M486) += -march=i486
cflags-$(CONFIG_M586) += -march=i586
cflags-$(CONFIG_M586TSC) += -march=i586
cflags-$(CONFIG_M586MMX) += -march=pentium-mmx
diff --git a/arch/x86/include/asm/vermagic.h b/arch/x86/include/asm/vermagic.h
index 5d47125..eda233a 100644
--- a/arch/x86/include/asm/vermagic.h
+++ b/arch/x86/include/asm/vermagic.h
@@ -5,10 +5,6 @@

#ifdef CONFIG_X86_64
/* X86_64 does not define MODULE_PROC_FAMILY */
-#elif defined CONFIG_M486SX
-#define MODULE_PROC_FAMILY "486SX "
-#elif defined CONFIG_M486
-#define MODULE_PROC_FAMILY "486 "
#elif defined CONFIG_M586
#define MODULE_PROC_FAMILY "586 "
#elif defined CONFIG_M586TSC
@@ -31,8 +27,6 @@
#define MODULE_PROC_FAMILY "K6 "
#elif defined CONFIG_MK7
#define MODULE_PROC_FAMILY "K7 "
-#elif defined CONFIG_MELAN
-#define MODULE_PROC_FAMILY "ELAN "
#elif defined CONFIG_MCRUSOE
#define MODULE_PROC_FAMILY "CRUSOE "
#elif defined CONFIG_MEFFICEON